Certain 1-hydroxy-3-substituted-6,6-dimethyl-6,6a,7,8,10,10a-hexahydro-9H-dibenzo[ b,d]pyran-9-ones have been found to be useful as a result of their effect on the central nervous system of mammals. A mixture of such compounds wherein the hydrogen atoms attached at the 6a- and 10a-positions are oriented trans to one another is particularly valuable in the treatment of anxiety, depression, and for providing analgesia. U.S. Pat. Nos. 3,953,603, 3,928,598 and 3,944,673 describe the use of such compounds, and draw particular attention to the use of the dl-racemic mixture of trans-1-hydroxy-3-(1,1-dimethylheptyl)-6,6-dimethyl-6,6a,7,8,10,10a-hexahy dro-9H-dibenzo[b,d]pyran-9-one, now generically referred to as Nabilone.
It recently has been discovered that separation of the dl-racemic mixture of both cis- and trans-isomers of the aforementioned hexahydrodibenzopyranones into the corresponding optically active isomers provides compounds with varying biological properties. In particular, one of the optical isomers of both cis and trans-hexahydrodibenzopyranones appears to be more active than the other optical isomer in its effect on the central nervous system of mammals. An object of this invention is thus to provide a process for preparing optically active isomers of certain cis- and trans-1-hydroxy-3-substituted-6,6-dimethyl-6,6a,7,8,10,10a-hexahydro-9H-di benzo[b,d]pyran-9-ones. A further object of the invention is to provide certain new compounds which are useful as intermediates in the preparation of such optically active hexahydrodibenzopyranones.